JUDY WOODRUFF: For much of the last three years, South Sudan has been embroiled in conflict with its northern neighbor. New violence erupted this week inside its borders, this time spurred by internal ethnic and political tensions, killing hundreds and sparking fears of further unrest.Jeff is back with that.

JEFFREY BROWN: The political crisis in the world's youngest nation deepened this week, raising fears of all-out civil war.Foreign nationals began evacuating and the United Nations sought to bolster its force there, after two Indian peacekeepers were killed yesterday. On Wednesday, President Obama ordered 45 American troops to reinforce U.S. Embassy security in Juba, the capital.

South Sudan broke off from Sudan in mid-2011. This conflict began as a power struggle between the country's president, Salva Kiir, and his former vice president, Riek Machar, whom he fired earlier this year.

They represent rival ethnic groups. Kiir is Dinka. Machar is Nuer. And some say that's fueling the violence.WOMAN: They are targeting Nuer particularly. And I don't know what the reason why this specific tribe is being targeted by the government forces.

JEFFREY BROWN: Kiir, who led the Sudan People's Liberation Army, or SPLA, in a long insurgency against Sudan, urged calm earlier this week.

But violence has continued. At least 500 people are reported dead, and 30,000 have been displaced. Late today, word came after a U.N. Security Council emergency session that Kiir and his former vice president will hold -- quote -- "unconditional talks" in an effort to defuse the crisis.

And with me now is Lesley Anne Warner, an Africa analyst at CNA, a not-for-profit research organization that provides analysis for the U.S. government and military.

Welcome to you.

LESLEY ANNE WARNER, CNA: Thank you.

JEFFREY BROWN: First, we have to remind people this is a -- this is a very new and clearly very volatile country.LESLEY ANNE WARNER: Yes, that's true.

So, South Sudan received its independence from Sudan in July of 2011. And this came after 23 years of civil war. And there had been a previous civil war from '56 to '72. But there had been great optimism when South Sudan eventually received its independence, although it was essentially starting as a very undeveloped state.

JEFFREY BROWN: Well, so what is the dynamic at work now? Does it seem more like political rivalries, or how much does it feel like ethnic divisions at work?

LESLEY ANNE WARNER: This current unrest started as a political dispute. And it has rapidly started it to take on elements of ethnic conflict, but it's not there yet.

But the issue is, once you cross the ethnic conflict line, it will be difficult to walk that back. So what started off as a dispute between Salva Kiir, President Salva Kiir, and his former vice president, Riek Machar, who he fired along with the rest of the cabinet over the summer in July, has become -- it started off with clashes in the capital city of Juba on Sunday, and has devolved into clashes in the rest of the -- in other parts of the country.

JEFFREY BROWN: And you are saying it would be hard to walk it back if it becomes -- and how strong are these ethnic divisions or how much of a factor is that in this new country?

LESLEY ANNE WARNER: It's a bit of a factor, but it's important not to reduce the conflict, this political conflict to Dinka vs. Nuer.

Dinka are the majority ethnic group in South Sudan. The second is the Nuer. There are several other ethnic groups in South Sudan. The reason the ethnic issue is important is that these groups were on opposing sides of the civil war in South Sudan. And Riek Machar himself was responsible.

When he split from the SPLA in 1991, he was responsible for some of the worst ethnic violence, or he was responsible for initiating some of the worst ethnic violence in South Sudan.

JEFFREY BROWN: This is also an oil-producing country, right? How much is that a factor in what is happening or what could happen?

LESLEY ANNE WARNER: It's -- the issue of oil is not a factor at this particular moment, but there is a potential that it could be an issue, because in areas where some of the clashes have broken out outside of Juba, there are reports of the SPLA, the military dividing along ethnic lines in Bentiu, which is the capital of Unity State, which is along the border with Sudan.

And a very heavy oil-producing area, and it's an area that suffered a lot of violence as a result of being in an oil-producing area during the civil war. There is also violence in Jonglei State, which is -- some oil is produced there as well, but not nearly as much as in Unity State.

And there is the potential that these armed movements may decide to capture the oil fields to be able to fund their continued rebellions.

JEFFREY BROWN: This is also within a very volatile region, right? So is the fear not only what happens within South Sudan, but whether it spreads?

LESLEY ANNE WARNER: I don't think that there is necessarily a fear that it will spread too much to the south. But there is a fear that it could destabilize Sudan, actually, just because, as you mentioned, oil is a variable in this -- oil is a potential future variable in this conflict.

And you have already seen in Sudan, when the oil was cut off between Sudan and South Sudan, because the oil is in -- most of the oil is in South Sudan and the pipeline goes out through Sudan, that there were anti-government protests that came very close to toppling the National Congress Party in Sudan. And you saw protests earlier this year as well. And so Sudan may also destabilize if oil is cut off from South Sudan.

JEFFREY BROWN: Now, we saw various steps being taken at the U.N., or at least discussions, and in Africa. What kind of leverage does the outside world, including the U.S., have, if any?

LESLEY ANNE WARNER: The outside world, especially the U.N., the African Union, the Intergovernmental Authority and Development, which is an East African regional community, they have a bit of leverage because of the role that the -- the instrumental role they played in brokering the peace agreement between Sudan and South Sudan signed in 2005.

However, at the same time, while they have diplomatic leverage, it is important to note that they don't necessarily have the military leverage to back that up, which is -- it is potentially problematic.

JEFFREY BROWN: And, briefly, does the U.S. have any particular interest at this point?

LESLEY ANNE WARNER: The U.S. has an interest because of the role that it played, along with other members of the international community, in brokering this peace.

But it's important to keep in mind that the U.S. has other priorities at play, not only globally, but also in Africa.JEFFREY BROWN: All right, Lesley Anne Warner, thanks so much.LESLEY ANNE WARNER: Thank you.

South Sudan: Machar Says Forces in Control of Most South Sudan Territory Amid Speculations of Attempted Juba Takeover

London — Forces of the Sudan People's Liberation Army (SPLA) loyal to the former South Sudan's vice president Riek Machar announced that they have taken control of the strategic oil rich region of Unity state, six days after fighting erupted in the capital, Juba.

Machar on Saturday told the BBC that his troops were now in control of "much of the country" including Bor, a strategic town, which is also the capital city of the largest state in the region, Jonglei.

The SPLA spokesperson, Col. Philip Aguer, on Saturday confirmed the fall of Unity state following a declaration by the SPLA Division 4 overall commander, Maj. Gen. Koang Chuol, that the region had fallen under the control of Machar, while in the state capital, Bentiu.

Regional leaders have been trying to initiate dialogue between Machar and South Sudan's president, Salva Kiir Mayardit. Machar however said Kiir had to step down first before a meaningful dialogue is launched to restore peace in the country. He also demanded the release of his colleagues arrested in the wake of the clashes last week.

Fighting reportedly started when misunderstanding ensued between members of the presidential guards inside a barrack in Juba.

Peter Adwok Nyaba, the former national minister of higher education, said the violence erupted when bodyguards loyal to Salva Kiir, predominantly of Dinka tried to disarm their Nuer colleagues in implementing the orders by the president Kiir.

Kiir however said the violence was a coup attempt by his political opponents.

With the violence also spreading to the other states, there are fears that the situation will further escalate despite government's assurances that the situation is under control.

Thousands of civilians, mostly from the Dinka ethnic group, are fleeing the capital Juba every day, crossing into Uganda, as rumors suggest that forces loyal to Riek Machar may attack the capital any time soon to take it from Kiir's forces.

Reports say Juba airport is also congested with thousands of people wanting to get into planes and leave.

MACHAR CONDEMNS AIR RAID BY UGANDAN AIRFORCE

The ex-vice president on Saturday also told the BBC that Ugandan military air force had carried out bombing around Bor town on Saturday, backing Kiir's forces, to retake Bor.

There were unconfirmed reports that one fighter jet was shot down. Also an American aircraft was hit while trying to evacuate their nationals from Bor, injuring four of its crew member, as reported by the BBC.

The Ugandan government has however denied having bombed Bor, although they confirmed the presence of their troops inside South Sudan "to rescue their nationals."

Thousands of civilians, predominantly from the Dinka ethnic group have sought refuge in the UNMISS compound in Bor, and across the country.

Machar's forces are also said to be in control of Mangala military base, which is about 30 kilometers from Juba, in Central Equatoria state, planning attack on the capital.

The US administration has warned that the international community will not condone or recognize any attempt by rebels to take over Juba.

"The United States and other partners are committed to the realization of South Sudan's full political, social, and economic potential, but make no mistake: these cooperative efforts will be undermined if political disputes drag the country back into senseless conflict and strife. Moreover, any armed attack on the capital will be seen as an attempt to achieve an unlawful usurpation of power, which would be universally condemned. Those who seek to take or hold power by violence or division of South Sudanese along ethnic lines will not have our support. Violence today will not pave the way for a more stable or prosperous tomorrow" US Secretary of State John Kerry said in a statement yesterday.